Our overall objective is to understand the structure of genetic regulatory signals in Escherichia coli. We are approaching this understanding through the following projects: 1) Structural analysis of the lac p-o region. We have isolated several lambda lac transducing phages which contain deletions defining the lac promoter-operator region from both sides, and we are using these phage DNA's to (a) relate the genetic location of the deletions to the repressor binding properties of the DNA's (b) determine the size of this region as well as the distance between different signals within the region via electron microscopic heteroduplex mapping and (c) purify lac p-o RNA by hybridization preparative to a complete sequence analysis of these signals. 2) Ribosome binding signals. We plan to isolate the lac z ribosome binding site by isolating lac RNA protected by ribosomes which are allowed to initiate but prevented from translocating due to antibiotic treatment. This RNA will be localized by hybridization to the above mentioned deletions and will hopefully be sequenced. We plan to isolate RNA corresponding to the intercistronic regions of the trp operon by hybridizing trp mRNA to lambda trp deletion DNA's defining these sites. 3) Trp regulatory mutants. We plan to isolate and characterize trp regulatory mutants, especially trp 0c mutations by using the lac phenotype of trp-lac fusions.